A billion years ago, the core of what was to become North America nearly ripped apart, creating a huge branched scar that extends from the tip of Lake Superior deep into the Midwest. Washington University in St. Louis scientists are using data from seismometers they placed across and along the rift to take a good hard look.
A three-dimensional seismic image of the mantle beneath the Lau Basin in the South Pacific just published in Nature has an intriguing anomaly. The image showed the least magma where the scientists expected to find the most. After considerable debate, they concluded that magma with a high water content was flushed so rapidly that it wasn’t showing up in the images.